Alloy and method of purifying same.



P. POETSCHKE.

ALLOY AND METHOD OF PURIFYING SAME.

APPLICATION FILED rm. 1, 191a.

1i %?8,7% v PatentedSept. 10,1918.

2 SHEETS-SHEET I.

Ql'lumargs P. POETSCHKE.

ALLOY AND METHOD OF PURIFYING SAME.

APPLICATION FILED FEB. 7, l9l8. LWSJWMD Patented Sept. 10,1918.

2 SHEETS-SHEET 2.

i M l aejwfe UNITED TATE PATENT OFFICE PAUL POE'ISCHKE, OF MILFORD,DELAWARE, ASSIGNOR TO L. D. GAULK COMPANY, OF MILFORD, DELAWARE, ACORPORATION OF DELAWARE.

ALLOY AND METHOD OF PURIFYING SAME.

Specification of Letters Patent.

Patented Sept. 10, 1918.

Application filed February 7, 1918. Serial No. 215,900.

-I do hereby declare the following to be a full, clear, and exactdescription of the invention, such as will enable others skilled in theart to which it appertains to make and use the same.

This invention relates to alloys and a method of purifying the same, andparticularly to dental alloys, and has for one object, the provision ofa purified form of alloy for filling teeth.

Dental alloys consist of silver and tin with smaller amounts of othermetals such as copper and zinc. Assold to dentists, they occur incomminuted form known as filings or shavings. For use, the comminutedalloy is amalgamated with mercury so as to yield a plastic mass capableof being condensed into a tooth cavity and hardenmg in sitw.

Dental alloys are manufactured by melting the various metals and castingthe same in bars, which are then comminuted so as to secure the filingsor shavings. The comminuted alloy is then annealed or heated for acertain time in order to improve its physical properties and adapt it tothe practical requirements of the dentist.

In the process of cutting and annealing it, it is impossible to avoidtarnishing of the comminuted alloy, which takes place through theoxidation and sulfidation of the alloy, thereby causing the alloy tolose its bright luster, the accumulation forming impurities. Thesesurface impurities also make it difiicult to amalgamate the alloy withmercury and the amalgam thus obtained isunclean. Moreover theseimpurities retard the setting of the amalgam.

To overcome these various defects, and provide an alloy which has abright silvery appearance, in contrast to the alloys made by the usualmethods and which have a dull or tarnished appearance, my presentinvention contemplates the manufacture of an alloy, in comminuted form,which is substantially free from surface oxidation and sulfidation, andthe efiects generally known as tarnishing of the metal.

Therefore, with the above objects in view, and as clearly understood bythose skilled in the art, the invention broadly consists in the method,and more definitely resides in removing the surface impurities ortarnish by immersing the comminuted and annealed alloy in a suitablesolution, having a solvent action on the surface impurities but not inany way adversely affecting the quality of the alloy or altering itschemical composition, and after such immersion thoroughly washing theallow and drying the same.

Apparatus for practising the present method is illustrateddiagrammatically in the accompanying drawing in which Figure 1illustrates a form of tray; Fig. 2 is a perspective of the tray having alayer of the material to be treated; Fig. 3 is a sectional elevation ofthe container or vessel in which the trays containing the material aresub merged in the cleaning solution; Fig. 4 is a perspective view of adraining rack for supporting the trays, and Fig. 5 is an elevationpartly in section of a drying device.

To secure the desired advantages and improvements in my alloy overcomminuted alloys of ordinary manufacture, I employ a solution ofacidified alcohol because such a solution accomplishes my purposes tobetter advantage than an aqueous solution of an acid; or of purealcohol; or of a mixture of Water, acid, and alcohol. I may use ethylalcohol, methyl alcohol, denatured alcohol, or a mixture thereof. As anacid of suitable character, I prefer to use hydrochloric acid. As aspecific example I might mention denatured alcohol approximately 98parts per volume and concentrated hydrochloricacid, approximately twoparts by volume.

The alloy to be purified is spread out upon trays 2, having a permeablebottom 3 which will permit circulation of the liquid and withoutallowing an appreciable amount of alloy to pass through. I prefer to usea cloth of suitable texture stretched over a substantial wooden frame.The trays are then immersed in a-tank 4, preferably of stoneware,containing the solution described above and permitted to remain for from18 to 24 hours or for such time as may be desired to clean the alloy.The trays are then removed from the solution, allowed to drain so as toremove the surplus solution, and then thoroughly washed in pure cleanwater in a tank.

The water is changed repeatedly until the final wash water is absolutelyfree from acid. The trays are placed upon a rack 5 and permitted todrain so as to remove the excess water, and in order to facilitatedrying they are dipped inpure alcohol or other solvent which is misciblewith water and has a lower boiling point. I may use ethyl, methyl, ordenatured alcohol, or mixtures thereof, for this purpose. After thesurplus alcohol has been allowed to drain off, the trays are placed in adrying chamber 6 having a heating coil or coils 7 and dried in a currentof warm air which is freed from dust by filtering through a screen 8therein. The velocity and temperature of the air is adjusted so as todry the alloy as rapidly as possible. I prefer to use a rapid current ofair at approximately 130 degrees F although this temperature may bevaried depending upon the size and shape of the alloy particles. Afterthe alloy is thoroughly dry it is transferred to convenient receptaclesand is then ready to be packed in suitable containers for distribution.

What is claimed is:

1. The process of purifying comminuted alloys consisting in subjectingthe comminuted alloy to treatment with acidified alcohol,washing inwater, dehydrating with alcohol, and drying in a'curre'nt of warm air.

2. The process of purifying comminuted alloys consisting in subjectingthe comminuted alloy contained in trays having a permeable bottom, totreatment with acidified alcohol, washing in water, dehydrating withalcohol, and drying in a current of warm air.

3. The process of purifying comminuted alloys consisting in subjectingthe comminuted alloy to the treatment of acidified alcohol, washing inwater, dehydrating with alcohol, and drying in a current of air. Intestimony whereof I afiix my signature.

PAUL POETSCHKE.

